School Achievement Test: evidence of validity of the writing subtest

The School achievement test (TDE) (Stein, 1994) assesses learning broadly through three subtests: reading, writing and arithmetic. The goal of this study was to evaluate the psychometric properties of the Writing Subtest, to evaluate the internal structure, items difficulty and discrimination, using Item response theory (IRT). The sample consisted of data from surveys conducted in four Brazilian states (N=1831). Results indicated that the writing subtest presents: (a) evidence of unidimensionality, (b) is composed by items of average difficulty and (c) with high discrimination capability. Moreover, it was observed that the Subtests discriminate satisfactorily students between first and third grade and, less appropriately, students from fourth, fifth and sixth grade. This set of results indicates that the Subtest presents evidence of validity, but requires refinement.